1. Field of the Invention
This invention relates to devices for stripping insulation from sections of an insulated electrical wire and more particularly to a hand-operated electrically heated miniature thermal wire stripper. The invention also relates to similar devices which may be used as a thermal implement for surgical operations, as well as to methods of fabrication of such devices.
2. Description of the Prior Art
The removal of insulation from electrical conducting wires in order to prepare the wires for further connection to associated circuitry has long been a difficult task in miniature circuitry where the wires are very small. The strong trend in the electronic business toward lighter and more compact electronic assemblies which have led to lighter and thinner electrical wires is well known. The smallest nick or even a shallow scratch, especially at the end of the insulation sleeve remaining on the conductor, increases the susceptibility of the wire to breakage. Also it is to be realized that, in very small conductors, the conductor is closely dimensioned to a given current capacity and the removal of the strand from a standard multi-strand conductor drastically changes the electrical characteristics of the conductor and destroys its effectiveness.
Devices for removing insulation from wires are generally known as wire strippers and may be broadly divided into two types. The first is a strictly mechanical device which grips the wire in two places, cuts the insulation between the two with a pair of opposed semi-circular cutting edges selected for the gauge of the wire, and pulls the cut insulation off the wire by laterally separating the two grip points. This mode of operating requires that a relatively long length of the insulated wire be available and that the wire be comparatively large, which usually precludes its use with either short lengths of wire or in miniature applications or in places were access is limited.
Even though the cutting blades are provided with a plurality of mated semicircular notches which are accurately sized for the different gauges of the wire, the most skilled assemblers must exercise great care to avoid damaging wires during the wire stripping operation. Even slightly touching or damaging one or two strands of a multi-strand miniature conductor destroys the operability of the conductor, since all conductors are generally designed with the current capacity closely corresponding to the size of the conductor. The stripper therefore is not entirely satisfactory as a tool in the assembling of circuits which are very small and wherein it is desired to strip insulated wires which are attached to electronic circuitry.
Another type of wire stripper known in the art avoids the danger of nicking or cutting wires and uses heat instead of a cutting blade to sever thermal insulation. Usually a signal heated filament is used to melt through the insulation. Such strippers are mostly used in preparing lengths of wires for production line assembly where the wires are precut to predetermined lengths and stripped to approximately 1/2 inch from each end. Special stripping operations are frequently done with small pliers, a knife or even with the fingernails of the assembler or repairman where cutting and stripping of insulation must be done in place in a miniature electrical circuit, as on a printed circuit board or the like. The wire must be handled with great caution to avoid damage to heat-sensitive components and it is clumsy and often impossible to use a conventional wire stripper where space is limited or in applications in miniature circuitry where it is desired to strip wire in place or with short lengths of wire to be stripped.
Thus the prime need today which is provided by the present invention is a thermal wire stripper that both severs the insulation and strips the insulation from a wire located in a limited access space in a single smooth hand operation without the danger of nicking, scratching, or burning or otherwise damaging the bare wire and with limited risk of damage to associated circuit components because of its small size and offset configuration.